The present invention relates to a rechargeable battery and a method for producing such a battery.
The requirements for the electrical charging and discharge performance for rechargeable batteries for vehicle applications are particularly stringent. This is particularly true for modern hybrid vehicles, in which large discharge currents are required, for example for acceleration, from relatively small energy storage batteries. Since the primary aim of hybrid vehicles is to improve economy by reducing the fuel consumption, a high-efficiency battery system is a fundamental precondition. The energy losses between the energy which can be drawn and the energy applied during charging must for this reason be kept as low as possible.
One of the major loss factors in rechargeable battery assemblies is the connection between the electrode packs in the individual cells and the pole bushings, and their connections to the intermediate cell connectors. A connection with high electrical conductivity and good mechanical robustness which is stable in the long term is necessary in order to ensure high energy efficiency of the battery system in the long term.
U.S. Pat. No. 3,844,841 and DE 698 00 524 T2 have disclosed rechargeable batteries in which the individual electrodes are provided with output lugs on their upper edge which have a circular hole in the region of their largest area extent. During assembly of the electrochemical cell (for example, nickel cadmium or nickel iron), electrodes of positive and negative polarity are stacked alternately one above the other, electrically isolated from one another by means of a fibrous separator. In this case, the positive output lugs and the negative output lugs point in opposite directions. The lugs and therefore all of the electrodes as well are mechanically passed through a positive and a negative pole link which, in the form of cylindrical bolts, pass through all the holes in the output lugs of the same polarity. These cylindrical bolts are threaded at their end. The output lugs are fixed by fitting a threaded nut to the pole end.
In order to allow the output lugs to be bundled and the holes in the output lugs to be aligned such that they are flush with one another, the output lugs must be mechanically angled, and must have different lengths, before being stacked. This necessitates a large number of different electrode types, whose manufacture is complex and expensive as a result of the handling of a large number of mechanically different parts.
For electrode arrangements with a relatively small number of individual electrodes, it is also known for the spaces between the output lugs to be filled by annular intermediate disks, in order to create a mechanically robust collector structure which is highly electrically conductive. The output lugs of the individual electrodes are electrically conductively firmly connected together, together with the intermediate disks, by tightening the closure nuts. A pole bolt is arranged approximately at the geometric center of the pole link, instead of an intermediate disk, and its lower end has a central opening in the same way as the intermediate disks. The pole bolt projects at right angles beyond the output lug bundle out of the electrode pack, and ensures that the electric current is output to the exterior from the cell.
The pole bolt is passed out of the housing to the exterior, for electrical purposes, in a gas-tight form by means of an arrangement comprising insulating, sealing and screw elements, so that no gas from the interior of the cell can penetrate to the exterior, and no gas from the exterior can penetrate into the interior of the cell via the bushing.
The electrical connection of the cells in a battery assembly to one another is made by means of cell connectors which are mechanically fitted in that part of the pole bolt which is located outside the cell. Alternatively, embodiments are also known, for example from the cited U.S. Pat. No. 3,844,841 and DE 698 00 524 T2, in which a pole output conductor, which makes electrical contact with an output lug bundle, is passed through the separating wall between adjacent cells.
It would be advantageous to provide an improved rechargeable battery having two or more cells which can be produced more easily and at a lower cost while nevertheless ensuring that the output lug bundles in the cell assembly are connected in a manner which is stable in the long term and is electrically highly conductive.